Method and apparatus for controlling the tension in tapes



Oct. 31, 1 G. T. w. GRIEVE ET AL 3,006,136

METHOD AND APPARATUS FOR CONTROLLING THE TENSION IN TAPES Filed March 7,1960 s Sheets-Sheet 1 B Mummy;

Oct. 31, 1961 G. T. w. GRIEVE ET AL 3,006,135

METHOD AND APPARATUS FOR CONTROLLING THE TENSION IN TAPES Filed March 7,1960 3 Sheets-Sheet 2 W W Attorney Oct. 31, 1 G. T. w. GRIEVE ET AL3,006,136

METHOD AND APPARATUS FOR CONTROLLING THE TENSION IN TAPES Filed March'7, 1960 3 Sheets-Sheet 3 v A) y )bg'plfl/ Mata WAUomey;

Unite States This invention relates to a method of and apparatus forcontrolling the tension in tapes, especially in tapes being drawn offfrom a roll or pad and lapped helically upon a core, for instance anelectric cable conductor, or wound spirally on a core as in themanufacture of wound capacitors.

When drawing off tape from a roll or pad (each hereinafter forconvenience referred to as a pad) it is desirable to use a pad of whichthe initial diameter is as as great as practicable. For example it iscommon practice for the paper cable maker to use pads of 16" diameterand in some cases pads of 25" diameter have been used. To preventoverrunm'ng of such pads it is essential to apply a braking load whichin the case of the 25" diameter pads may impose upon the paper beingdrawn off a tension of about 1 /2 lbs. As more and more tape is drawnoff from the pad the braking load necessary to prevent overrunningnaturally diminishes though not proportionally to the reduction in paddiameter. At the same time the tension in the paper per unit ofretarding torque imposed on the coil increases. Numerous devices havebeen suggested for effecting a gradual reduction in the braking load asthe pad diameter is reduced, with the object of ensuring that thetension in the tape as it runs on to the core on which it is to belapped or wound remains substantially constant. Other devices purportingto ensure reasonably constant tension in the tape irrespective of paddiameter involve imparting an additional retarding force to the tapeafter it has left the pad and for the gradual reduction of thisadditional tensile loading of the tape to correspond with the additionaltensile load due to the gradual reduction of pad diameter. In practiceit is found that with both forms, errors occur and that the percentageerror increases as the theoretical lapping or winding tensiondiminishes. Accordingly, existing systems of tape tension control,though reasonably satisfactory :for tapes of the kind most generallyused by cable makers, e.g. for pape tapes having a width of 1 inch ormore and a thickness of about four mils, are not satisfactory fornarrower and thinner tapes.

Moreover, in the case of impregnated paper insulated cables, it isdesirable that all the tapes used to build up the dielectric wall shallbe applied with the same tensile stressfor example some particular valueof tensile stress within the range 500 to 1,000 lbs. per square inch.While it is possible to maintain an approximation to such a stress whenlapping thick and wide papers it becomes difiicult to do so when lappingthin tapes of narrow width unless pads of small diameter are used-whichis uneconomical as it reduces the load factor of the machine. This willbe appreciated if one considers for instance a paper tape of .62 inchwidth and 3 mils thickness. To lap such a tape at a definite stress ofwithin the range of say, 500 to 1,000 lbs/sq. in. involves running thetape on to the conductor under a tension within the range 14 to 29 ozs.But to prevent overrunning of a pad of 25 inch diameter may require abraking torque which imposes initially a tension of 24 ozs. in thepaper. As the pad reduces in diameter the tension in the paper necessary to overcome this braking torque (if the braking atent i"- torque benot reduced in proportion) increasesin which event it becomes impossibleto maintain the stress in the lapped paper at the desired figure.

The present invention provides an improved method of and apparatus forcontrolling the tension in tape as it is being lapped or wrapped orotherwise wound on a core which reduces to a substantial extent thedifiiculties inherent in existing devices and permits of the use oflarge pads of thin tape of narrow width.

In accordance with our invention the tension in the tape as it runs onto the core on which it is to be lapped or wrapped or otherwise wound ismaintained at a value approximating the desired value by applying aretarding force to the tape in excess of the winding tension andapplying an advancing force to the tape between the point or points ofapplication of the retarding force and the Winding point and adjustingthe value of the one applied force relative to the other to give theapproximate residual winding tension required.

The retarding force may be due principally to the retarding torqueexerted on the coil due to brake action and bearing friction or to acombination of such torque and to the frictional retarding effect of abrake or brakes acting directly on the linearly traveling tape.Reduction of the tension in the tape to the required residual value andits maintenance at such value within reasonably close limits as windingproceeds may be achieved either by maintaining the retarding forceconstant within reasonably close limits as by gradually reducing thebrake action on the coil as it reduces in diameter, or by allowing theretarding force to vary as by omitting to reduce the braking action onthe coil as it reduces in diameter and varying the value of theadvancing force applied to the tape, or by a combination of bothmethods. We prefer to maintain the value of the retarding force asconstant as practicable and to maintain the residual tension in the tapeat the required value by initially adjusting the value of the advancingforce applied to the tape. This preferred method of operation has theimportant advantage that any errors in the value of the retarding forcethat may occur as winding proceeds are automatically reduced and appearin the residual winding tension merely as a fraction of thecorresponding errors in the retarding force, this fraction correspondingto the ratio between the residual tension and the initial tension in thetape.

The invention also includes apparatus for carrying out the aforesaidmethod of controlling the winding tension which comprises means forapplying an advancing force of variable value to the tape as it travelsto the core on which it is to be wound, comprising a driving member, forexample a capstan or a belt, acting upon a surface of the tape and meansfor imparting to the surface of the driving member in engagement with asurface of the tape a speed of travel in excess of that of the tape sothat there is slip between the tape and its driving member. Where thedriving member is a capstan its peripheral speed of travel is in excessof that of the tape and where the driving member is a belt its linealspeed of travel is in excess of that of the tape. We have found itbetter from the point of View of obtaining a more accurate control ofthe residual tension for the speed of the driving surface to exceed thatof the driven tape very considerably-the speed of the driver beingpreferably at least three to four times as fast as that of thetape. As adriving member We prefer to employ a driven capstan. The capstan ispreferably of ceramic material but at least its driving surface may beof a metal which is inherently corrosion proof, for example the capstanmay be of stainless steel, or it may be plated on its peripheral surfacewith a metal which is inherently corrosion proof for example nickel orrhodium.

3 We prefer to use a motor-driven capstan rather than one driven by adrive taken from the winding head itself.

Control of the value of the advancing force applied to the tape by sucha capstan is obtained by varying the arc of contact between the capstanand the tape. This may be done by means of guide rollers on the approachand departure sides of the capstan, these guide rollers and/ or thecapstan being movable, the one relative to the other. In a preferredarrangement there is a guide roller on the approach side of the capstanand a second guide roller on the departure side. Tape approaches underthe approach guide roller and passes partly round the capstan and rounda skewed roller having its axis at an angle of 4550 to the axis of thecapstan and back round the capstan and ofif under the departure guideroller. The diameter of the skewed roller is such as to ensure that thesecond Wrap of tape round the capstan is displaced from the first to anextent to leave a safe gap between their neighbouring edges. For examplethe diameter of the skewed roller may be /2 the capstan diameter, givinga lateral displacement of the second wrap to the first wrap equal to thecapstan diameter. With this preferred arrangement by providing formovement of the capstan and its skewed roller relative to the approachand departure rollers in a direction perpendicular to a plane tangentialto the approach and departure guide rollers, the aggregate arc ofcontact between the tape and the capstan may be varied from about 60 to320. Alternatively, the approach and departure guide rollers may beswung to a limited extent about the capstan.

An example of a preferred form of apparatus for controlling tension intape in accordance with the invention will now be described withreference to the accompanying drawings, wherein:

FIGURE 1 is a plan view, partly broken away, of an arm of a cable paperlapping machine carrying means for applying a braking torque to thepaper tape and means for applying an advancing force to the tape,

FIGURE 2 is a side elevation, partly in section, of the means shown inFIGURE 1 for applying the braking torque, but drawn to a large-r scale,

FIGURE 3 is an enlarged plan View of the means shown in FIGURE 1 forapplying the advancing force to the tape and,

FIGURE 4 is a sectional view of the apparatus of FIGURE 3 taken alongthe line IVIV thereof.

FIGURE 1 shows the invention applied to a cable paper lapping machine ofthe kind in which paper pads 1 are carried bodily around alongitudinally advancing cable core 2. The spindle 3 for the pad 1 ismounted on an arm 4 of the machine and tape 5 as it is taken from thepad passes under a roller 6 forming part of the gear for controlling thebraking torque applied to the pad, then through apparatus for applyingan advancing force to the tape and finally on to the cable core 2.

The gear for controlling the braking torque applied to the pad is shownin FIGURES 1 and 2.. The axle 7 of the roller 6 under which the tapepasses is supported on the outer end of an arm 8 formed on a spindle 9rotatably mounted on the arm 4 of the machine. The spindle 9 has formedon it a second arm 10 and to the outer end of this is attached, by ahinge 1 1, a wedge member 12 having two inclined faces. Two crankedlevers 13 are pivotally mounted on a support 14 fixed to the arm 4 ofthe machine and on one end of each lever 13 is rotatably mounted aroller 15. Bridging the two levers 13 between the support 14 and therollers is a compression spring 16 adjustable by a screw 17. The ends ofthe levers 13 remote from the rollers are each. provided with a disc 18having pads 19 of oiled felt on their opposed fiat faces. A metal brakedisc 20 is fastened to one end of the pad spindle 3 and the felt pads 19are arranged one on each side of the metal brake disc 20 and inregistration with one another.

The retarding force applied to the tape 5 by the pad braking means isarranged to be in excess of the lapping tension and is maintainedconstant within reasonably close limits as the pad reduces in diameterby suitably reducing the brake action on the pad. The latter is effectedas follows: When the tape 5 is applied from a full pad the spring 16acting through the levers 13 is arranged to press the felt pads 19 intocontact with the metal brake disc 20 to provide the required brakingtorque, the rollers 15 being out of contact with the inclined faces ofthe wedge 12. As the diameter of the pad reduces, any slight increase inthe tension of the tape is transmitted to the roller 6 and produces aslight rotation of the spindle 9. This causes the arm 10 to move in adirection to drive the wedge member 12 in between the rollers 15 so thatthe inclined faces of the wedge 12 make contact with the rollers 15 andurge the rollers 15 apart slightly, thereby producing a slight pivotalmovement of the levers 13 in opposition to the spring 16 and slightlyrelieving the pressure of the oiled felt pads 19 on the brake disc 20and reducing the braking load. By careful initial adjustment of thisgear the retarding force applied to the tape by the brake as the padreduces in diameter may be kept reasonably constant.

After leaving the roller 6 the tape 5 is guided over a roller 21 to theapparatus for applying an advancing force to the tape. This is shown inFIGURES 3 and 4. It comprises a base-plate 22 fixed to the arm 4 of themachine and supporting the casing 23 of an electric motor whose spindle24 carries a capstan 25 of ceramic material. Also fixed to thebase-plate 22 is a bracket 26 carrying at a distance from the capstan 25a freely rotatable roller 27, the axis of which is set at an angle ofabout 45 to the axis of the capstan. There is a guide roller 23 on theapproach side of the capstan 25 and a guide roller 29 on the departureside. These rollers are freely rotatably mounted on a U-sh-aped plate 30having a threaded bore through which passes a lead screw 31 rotatablyheld by a bracket 32 fixed to the base-plate 22. The lead screw isprovided with a handle 33 at its end remote from the screw-thread. Aclamping screw 34 and nut 35 are provided to clamp the U shaped plate 30in any desired position on the threaded portion of the lead screw. Tomove the U-shaped plate 36 from one position to another along the leadscrew the clamping nut 35 is loosened and the handle 33 of the leadscrew is turned until the U-shaped plate 30 is in the new position, whenthe clamping nut 35 is tightened. Two bars 36 parallel one with theother guide the U- shaped plate 30'.

The tape 5, after passing over the roller 21, passes under the approachguide roller 28 and passes partly round the capstan 25 and the skewedroller 27, back partly round the capstan and ofi under the departureroller 29. From there it is led over a roller 37 and then under a roller38 set at an angle such that the tape is applied tangentially to thecore 2 (see also FIGURE 1).

The U-shaped plate 30 and rollers 28 and 29 are shown in FIGURE 3 infull lines in the position of maximum wrap of the tape on the capstan25, in which the aggregate arc of contact between the tape and thecapstan is about 320. In the position shown in chain dotted lines inFIGURE 3 the aggregate arc of contact between the tape and the capstanis the minimum value, about 60. It will be appreciated that any are ofcontact between the tape and the capstan within the range 60 to 320 maybe obtained by adjustment of the position of the U-shaped plate 30 onthe threaded part of the lead screw 31. Then by using a motor whichdrives the capstan at a peripheral speed in excess of that of thetape,'for example at a speed at least three times as fast as the tapeand by suitable adjustment of the aggregate arc of contact, an advancingforce may be applied to the tape which reduces the initial tension inthe tape to the required residual value for lapping on the core. For

r. as

example the aggregate arc of contact may be adjusted so that the tensionin the tape is reduced from a value of say 4 lbs. plus or minus say 4ozs. on the input side of the capstan to a value of say 4 ozs. plus orminus 4 oz. on the output side of the capstan.

What we claim as our invention is:

1. A method of controlling the tension in tape as it runs on to a coreon which it is to be wound, which comprises applying a retarding forceto the tape in excess of the winding tension, applying an advancingforce to the tape between the point or points of application of theretarding force and the winding point, and adjusting the value of theone applied force relative to the other to give the approximate residualwinding tension required.

2. Apparatus for controlling the tension in tape as it runs on to a coreon which it is to be wound, comprising means for applying a retardingforce to the tape, a driving member for acting upon a surface of thetape between the point or points of application of the retarding forceand the winding point, and means for imparting to the surface of thedriving member in engagernent with a surface of the tape a speed oftravel in excess of that of the tape.

3. Apparatus for controlling the tension in tape as it runs on to a coreon which it is to be Wound, comprising means for applying a retardingforce to the tape, a capstan for acting upon a surface of the tapebetween the point or points of application of the retarding force andthe winding point, and means for driving the capstan at a peripheralspeed of travel in excess of that of the tape.

4. Apparatus as claimed in claim 3, in which the capstan is of ceramicmaterial.

5. Apparatus as claimed in claim 3, in which at least the drivingsurface of the capstan is of metal which is inherently corrosion proof.

6. Apparatus as claimed in claim 3 comprising a driving motor solely forthe capstan.

7. Apparatus as claimed in claim 2 in which the means for imparting tothe surface of the driving member in engagement with the tape a speed oftravel in excess of that of the tape is adapted to drive said surface ofthe driving member at a speed at least three times as fast as the speedof the surface of the tape.

8. Apparatus for controlling the tension in tape as it runs on to a coreon which it is to be wound, comprising means for applying a retardingforce to the tape, a capstan for acting upon a surface of the tapebetween the point or points of application of the retarding force andthe winding point, a pair of guide rollers, one on the approach side ofthe capstan and one on the departure side, means for adjusting the guiderollers relative to the capstan to vary the aggregate arc of contactbetween the tape and the capstan, and means for driving the capstan at aperipheral speed of travel in excess of the tape speed so that there isslip between the tape and the capstan.

9. Apparatus for controlling the tension in tape as it runs on to a coreon which it is to be wound, comprising means for applying a retardingforce to the tape, a capstan for acting upon a surface of the tapebetween the point or points of application of the retarding force andthe winding point, a guide roller on the approach side of the capstanand a second guide roller on the departure side, and a skewed rollhaving its axis at an angle of 45 50 to the axis of the capstan, wherebythe tape approaches under the approach guide roller and passes partlyround the capstan and around the skewed roller, back partly around thecapstan and otf under the departure guide roller.

10. Apparatus as claimed in claim 9 in which the diameter of the skewedroller is /2 the capstan diameter.

11. Apparatus as claimed in claim 9 in which means are provided foreffecting relative movement between the capstan and its skewed roller onthe one hand and the approach and departure guide rollers on the otherhand in a direction perpendicular to a plane tangential to the approachand departure guide rollers.

12. In a cable lapping machine of the kind in which pads of tape arecarried on arms bodily around a longitudinally advancing cable core,apparatus as claimed in claim 8 carried on an arm carrying a pad, thecapstan being fixed relative to said arm and the approach and departureguide rollers being mounted on a slide adjustable with respect -to saidarm to permit the wrap on the capstan to be adjusted to a value whichwill result in the initial tension in the tape being reduced to therequired residual value.

References Cited in the file of this patent UNITED STATES PATENTS2,253,740 Van Hook Aug. 26, 1941 2,462,043 Neidel Feb. 15, 19492,623,345 Grieve Dec. 30, 1952

